4b (diversity, selection and classification)

Question 1

what is diploid?
what is haploid?

Answer 1

2n chromosomes- 2 of each chromosome one from each parent
n number of chromosomes- one of each

Question 2

what does fertilisation is random mean? what does it result in?

Answer 2

any sperm can fertilise any egg
results in zygotes w diff combo of chromosomes to both parents

Question 3

what happens in meiosis?

Answer 3

interphase- DNA replication
Meiosis 1- homologous chromosomes separated from each other
meiosis 2- sister chromatids become separated
4 genetically different haploid cells are produced

Question 4

what happens in meiosis 1?

Answer 4

prophase 1- nuclear envelope breaks down, spindle fibres form from centrioles, homologous chromosomes wrap around each other, crossing over occurs leading to variation

metaphase 1- chromosomes line up next to homologous partner at equator, centromeres attach to spindle fibres, chromosomes randomly organised on either side of equator- independent assortment leads to variation

anaphase 1- separation of homologous chromosomes to opposite poles, one of each pair will end up on either side so variation

telophase 1- reforming of the nuclear envelope

cytokinesis- cytoplasm splits

Question 5

what happens in crossing over?

Answer 5

homologous chromosomes associate
chiasmata form
equal lengths of non-sister chromatids/ alleles are exchanged
producing new combinations of alleles

Question 6

what happens in meiosis 2?

Answer 6

prophase 2- dna becomes condensed and visible again, nuclear membrane disintegrates, spindle fibres form, chromosomes are not identical

metaphase 2- chromosomes line up at centre attached by spindle fibres, randomly assorted to either side so variation

anaphase 2- genetically diff chromatids randomly segregated to opposite poles by spindle fibres contracting

telophase 2- nuclei reform

cytokinesis- cell splits, 4 cells, haploid

Question 7

how does crossing over lead to variation?

Answer 7

in meiosis 1, homologous chromosomes pair up
chromatids twist around each other and bits of chromatids swap over
chromatids still contain same genes but diff combos of alleles

Question 8

how does independent segregation lead to variation?

Answer 8

each homologous pair has 1 maternal and 1 paternal
when separated in meiosis1, chromosomes end up randomly in daughter cells
so 4 daughter cells have completely diff combos of maternal and paternal chromosomes

Question 9

different outcome of meiosis/ mitosis

Answer 9

meiosis:
produces cells with half no of chromosomes as parent
daughter cells genetically diff from each other and parent
4 daughter cells

mitosis:
produces cells with same no of chromosomes as parent
daughter cells genetically identical to each other and parent
2 daughter cells

Question 10

why are mules infertile?

Answer 10

homologous chromosomes cant associate because they arent the same size
also, odd number so one left unpaired

mitosis can still occur though as pairing up of homologous chromosomes is only in meiosis

Question 11

what is a chromosome mutation?

Answer 11

variations in number of whole chromosomes or parts of chromosomes
caused by errors in meiosis
lead to inherited conditions as the errors are in gametes

Question 12

example of chromosome mutation

Answer 12

non-disjunction
leads to down’s syndrome
chromosome 21 fails to separate properly in meiosis so one cell gets extra copy and one gets none
when this gamete fuses with another, results in 3 copies of chromosome 21

Question 13

what is a mutation?

Answer 13

change in DNA base sequence
means amino acid sequence and protein are altered
(diff amino acid coded for so diff protein)

Question 14

what is a mutagen?
eg

Answer 14

physical/ chemical agent that changes genetic material and increases frequency of mutations above normal background level
ionising radiation (gamma)
uv
nitrosamines in tobacco
viruses
mustard gas
benzene- industrial solvent

Question 15

what is a substitution?

Answer 15

a single nucleotide base is replaced by another

Question 16

what is a silent mutation?

Answer 16

no change to the primary structure of the polypeptide despite having change in base
due to degenerate nature of dna- substitution may still code for same amino acid

Question 17

what is a deletion?
what effect does it have?

Answer 17

one base is deleted
knock on effect of all triplet codes
reading frame splits sequence into non-overlapping sections but deletion causes frame shift so every amino acid downstream of the mutation is effected.

Question 18

what has happened if the chromosome number has halved?

Answer 18

meiosis

Question 19

what has happened if the chromosome number has doubled?

Answer 19

fertilisation

Question 20

what has happened if the chromosome number stays the same?

Answer 20

mitosis

Question 21

what is non-disjunction?

Answer 21

the chromosomes fail to separate properly

Question 22

what is aneuploidy?

Answer 22

the presence of an abnormal number of chromosomes in a cell eg having 45 or 47 chromosomes when 46 is expected in a human cell

Question 23

What 4 things lead to variation?

Answer 23

2n possible combinations of maternal and paternal chromosomes
crossing over in meiosis 1
independent segregation in meiosis
random fusion of haploid gametes at fertilisation

Question 24

what is genetic diversity?

Answer 24

number of different alleles of genes in a species or population

Question 25

what is a population?

Answer 25

a group of organisms of one species living in a particular habitat

Question 26

what is diversity within a population increased by?

Answer 26

mutations in dna forming new alleles diff alleles being introduced into a population when individuals from another population migrate into them and reproduce- gene flow

Question 27

what is a genetic bottleneck?

Answer 27

an event that causes a big reduction in a population eg when a large no of organisms in a pop die before reproducing this reduces no of diff alleles in gene pool so decreases genetic diversity survivors reproduce and larger pop created from few individuals eg northern elephant seals

Question 28

what is the founder effect? what can cause it to occur?

Answer 28

type of genetic bottleneck few organisms from pop start new colony from small no of alleles in initial gene pool frequency of each allele in new colony diff to frequency of those alleles in og pop. eg initially rare allele might become common now- may lead to higher incidence of genetic diversity can occur due to migration leading to geographical separation or if new colony separated from og pop for another reason eg religion eg the amish

Question 29

what is natural selection?

Answer 29

mutation may result in new allele that is beneficial (so different reproductive success) organism is better competetor and more likely to survive and reproduce and pass on useful allele so greater proportion of next gen have it so more likely to surive breed pass on so freq of allele increases from gen to gen leading to evolution

Question 30

what are behavioural adaptations? what are physiological adaptations? what are anatomical adaptations? examples

Answer 30

ways organisms act that increase chance of survival eg possums play dead if threatened processes inside organisms body that increase chance of survival eg bears hibernate and lower rate of metabolism to conserve energy so dont need to eat structural features of organisms body that increase chance of survival eg whales have blubber to keep warm

Question 31

what is phylogeny? what is a phytogenic tree?

Answer 31

study of evolutionary history of groups of organisms . tells us whos related and how closely shows how all organisms adapted from one common ancestor closely related species diverged away most recently so branches are closer together

Question 32

what is taxonomy?

Answer 32

science of classification involves naming organisms and organising them into groups so easier to identify and study

Question 33

how are organisms classified?

Answer 33

a hierarchy of groups with no overlaps grouped according to evolutionary origins

Question 34

what is a hierarchy

Answer 34

groups within groups with no overlap- belong to one group at each level

Question 35

what are the three domains?

Answer 35

Eukaryota bacteria archaea (booklet in book explaining each one. need to know?)

Question 36

order of taxa

Answer 36

domain kingdom phylum class order family genus species

Question 37

what is a species?

Answer 37

group of similar organisms able to reproduce to give fertile offspring

Question 38

what is the binomial naming system?

Answer 38

named by genus species so scientists across world can communicate avoids confusion of common names

Question 39

what is courtship behaviour? what are the 2 types?

Answer 39

behaviour carried out by organisms to attract a mate of the right species can be simple eg releasing chemicals or complex eg displays

Question 40

what does courtship behaviour is species specific mean? why is courtship behaviour species specific? what can it be used for because of this?

Answer 40

only members of same species do and respond to that courtship behaviour allows members of same species to recognise each other, prevent inbreeding and make reproduction more successful (check book for more) can be used to classify organisms- more similar behaviour means more closely related

Question 41

examples of courtship behaviour

Answer 41

fireflies-pulses of light- pattern specific to species crickets make sounds- diff pattern diff species male peacocks show off colourful tails male butterflies use chemicals to attract females- only those of correct species respond

Question 42

technologies useful for clarifying evolutionary relationships

Answer 42

genome sequencing comparing amino acid sequence immunological comparisons

Question 43

how can genome sequencing be used to clarify evolutionary relationships?

Answer 43

can compare dna base sequence of one organism to that of another to see how closely related they are more closely related -more similar order of bases lead to reclassification of some animals

Question 44

how can comparing amino acid sequence be used to clarify evolutionary relationships?

Answer 44

proteins made of amino acids sequence of amino acids coded for by base sequence in dna related organisms have similar amino acid sequences in proteins

Question 45

how can immunological comparisons be used to clarify evolutionary relationships?

Answer 45

similar antibodies bind to same protein antibodies of human version of a protein (anti-human antibodies) added to isolated sample of another species, any proteins like the humans will bind. more bound means more closely related

Question 46

old ways of estimating genetic diversity vs new ways

Answer 46

- early estimates made by looking at frequency of measurable/ observable characteristics in a pop- alleles determine characteristics so wide variety of characteristics means lots of alleles so diverse - now, gene technologies have been developed to measure directly and give more accurate estimate that can be compared easily: - diff alleles have slightly diff base seq so compare base seq in diff organisms to see how many alleles of that gene in that pop - diff alleles produce slightly diff mRNA seq and may produce proteins w diff amino acid seq so can be compared

Question 47

what is variation? what is it caused by?

Answer 47

difference that exists between individuals genetic factors due to diff genes between species and diff alleles within species differences in environment most variation due to mix of both

Question 48

why should you use a random sample when studying variation? how do you do this?

Answer 48

so its not biased and accurately represents whole population eg pick random sample site by dividing field into coordinates and using number gen

Question 49

what can we use to tell if theres variation between samples?

Answer 49

mean avg most samples have values either side so end up with bell shaped normal distribution curve

Question 50

what is standard deviation? what are error bars?

Answer 50

tells u how much values in a sample vary- measure of spread of values about the mean large sd- big variation vice versa sd plotted on graph/ chart of mean values using error bars which extend 1 sd above and below mean- longer bar means larger sd so more spread out

Question 51

what is biodiversity? what is a habitat? what is a community?

Answer 51

variety of living organisms in an area place where an organism lives all the populations of diff species in a habitat

Question 52

what is local biodiversity? what is global biodiversity?

Answer 52

variety of diff species in a small habitat variety of species on earth

Question 53

What is species richness? how can it be worked out?

Answer 53

a measure of the number of different species in a community. it is a simple measure of diversity worked out by taking random samples of a community and counting the no of diff species

Question 54

other than species richness, what else is a measure of biodiversity?

Answer 54

Index of diversity which takes into account the number of species in a community (species richness) and the abundance of each species (population size)

Question 55

how do you calculate the index of diversity?

Answer 55

d= N(N-1) / E n(n-1) N is the total no of organisms of all species n is the total number of organisms of 1 species E is the sum of higher number means more diverse. if all individuals are the same species the index of diversity is 1

Question 56

Which agricultural practices reduce biodiversity?

Answer 56

woodland clearance- done to increase area of farmland but directly decreases no of trees and sometimes species of trees. destroys habitats so species lose shelter/ food and have to migrate/ die so biodiversity decreases Hedgerow removal- done to increase area of farmland. same as woodland clearance Pesticides- kills pests so directly reduce biodiversity and any species that feed on them lose food source so their number decrease too Herbicides- kill weeds so decreases plant diversity and reduces no of organisms that feed on the weeds monoculture- field of one type of plant. reduces biodiversity directly and also supports fewer organisms. also depletes soil of certain minerals. help- crop rotation

Question 57

what are direct and indirect ways that farmers decrease biodiversity

Answer 57

**direct:** remove hedgerows woodland clearance overgrazing monoculture pesticides directly kill pests herbicides **indirect:** pesticides kill animals that feed on pests inorganic fertilisers effluent runoff into water not rotating crops

Question 58

examples of conservation schemes to protect biodiversity

Answer 58

giving legal protection to endangered species as well as breeding programmes creating protected areas such as SSSIs (sites of special scientific interest) and AONBs (areas of outstanding natural beauty). these restrict further development the environmental stewardship scheme encourages farmers to conserve biodiversity eg by replanting hedgerows reduction of CO2 emissions and deforestation by some governments

Question 59

what is directional selection? eg?

Answer 59

individuals with alleles for characteristics of an extreme type are more likely to survive and reproduce. could be resopnse to change in environment eg bacteria evolving antibiotic resistance- some have alleles giving them ar, pop exposed to antibiotic which kills bacteria wo ar, resistant survive and pass on useful allele so offspring have ar, after some time, most of pop will carry ar allele

Question 60

what is stabilising selection? eg?

Answer 60

individuals with alleles for characteristics towards the middle are more likely to survive and reproduce. occurs when environment isnt changing and reduces range of poss characteristics eg human birth weight- humans have range of birth weights but very small are less likely to survive as its hard to maintain body temp and large babies are less likely to survive as hard to birth. medium sized is most favourable so weight of human babies tends to shift to middle

Question 61

what is disruptive selection? eg?

Answer 61

favours the 2 extremes of a phenotype. occurs in environ that favours more than one phenotype. selection pressures select against avg phenotype eg Atlantic salmon, coloured oysters

Question 62

what is dna hybridisation? what are the steps of dna hybridisation?

Answer 62

- used to compare dna of 2 species to see how closely related they are 1) take dna from 2 species and radioactively label 1 and mix the 2 species 2) heat to break H bonds and separate strands. - let them cool so strands can combine w others with complimentary sequence 3) some double strands that reform will be hybrids 4) more complimentary the hybrid dna sequence, more H bonds as more complimentary so higher temp needed to separate the H bonds 5) higher the temp. more similar the base sequence so more closely related

Question 63

practical in this topic?

Answer 63

aseptic technique

Question 64

what is independent segregation?

Answer 64

describes how homologous chromosomes separate in meiosis, ensuring each gamete receives one of each chromosome pair.

Question 65

what is random assortment?

Answer 65

refers to the random orientation of chromosome pairs at the metaphase plate, influencing the combination of maternal and paternal chromosomes that can end up in a gamete.